class Singleton(type):
    _instances = {}
    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super().__call__(*args, **kwargs)
        return cls._instances[cls]

class MyClass(metaclass=Singleton):
    pass

# Usage:
obj1 = MyClass()
obj2 = MyClass()
res = obj1 is obj2  # True
print(res)  # 输出: True